Apparatus for shaping tube elbows



Sept. 25, 1956 A. HUET APPARATUS FOR SHAPING TUBE ELBOWS Filed July 7, 1954 INVEN TOR.

United States Patent APPARATUS FoR SHAPING TUBE ELBOWS Andre Huet, Paris, France, assignor to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application July 7, 1954, SerialNo. 441,778

2 Claims. (Cl.-15 3-48) The present invention relates to apparatus for working metallic tubes and particularly to dies for forming return bends having tube legs extending in closely spaced parallel relation from the bend or elbow.

Tube elbows or hair-pin tubes that are produced by bending a straight tube and then reducing the radius of curvature of the bend by bringing together the tube legs extending from the elbow are always not accurately circular over 180 degrees and may have more or less angular varieties of shoulders, while the section of the tube in the interior of the elbow may be somewhat ovalized. Finally, the tube legs of the bend are not always accurately parallel. If it is desired to obtain hair-pin elbow tubes of perfect shape, with circular section and parallel tube legs, it is then necessary to submit the elbow obtained by the process just mentioned to a final shaping operation.

Moreover, it has been proposed when it is desired to bend tubes with rather thin walls to begin by ovalizing the tube before the bending operation in such a way as to reduce its moment of inertia. The final bend obtained is then of oval section and where it is necessary to restore a circular section to this bend, a final shaping operation is required.

The present invention applies to an apparatus including matrices and a punch for the final shaping of tube elbows.

The particularity of this process rests in that the elbow it is desired to shape is placed between matrices which will support the piece between the legs of the elbow, and which has half-grooves that adapt themselves only to the interior portion of this elbow, and which the shaping punch, used in combination with these matrices adapting itself to the outer portion of the elbow, slides inside the matrices during the shaping operation, to apply on the exterior of the rectilinear branches of the bend and finally to encase the whole exterior portion of the bend.

The whole process is accompanied, preferably by a uniform heating of the bend to be treated at a relatively low temperature to avoid any flattening, preferably with the exception of a straight area which will remain cool and which is in the internal portion of the bend, taking support on the projection of the semi-matrices which shape the said internal portion.

Figure 1 illustrates the matrices and punch in transverse section, an elbow to be shaped being shown in place in the apparatus;

Figure 2 is a section on line 22 of Figure 1 the upper semi-matrix having been removed, the elbow being shown in place in the lower semi-matrix before the shaping operation;

Figure 3 is a view similar to Figure 2 but after shifting of the punch to effect the shaping operation; and

Figure 4 is a variation of Figure 3 in the case where a bifurcated tube is the workpiece.

The tube bend A which is to be shaped is placed between two die halves 10, 12 (Figure 1) having projections 2,764,216 Patented Seph 25,.1e5s

.2 r 14, 16 respectively, that are engageable between the tube legs B, C and have end faces 15 shaped for adapting the tube exactly to the shape of the crotch that :is to be formed between the legs of the :final bend .A. Each matrix has grooves .20, 21, 22, .23, forming complementary parts of semi-circular.recesses'which encasexandshape the inside or crotch .faces of the tube legs B, 'C at .the :bend.

. Between the die halves 10, 12 enclosing the tube them! A, a punch 24 is engageable and this has a semi-circular groove 26 capable of 'encasing the whole-exterior portion of the elbow as can be seen in Figure12, this groove extending along the punch fingers 27, .28 which thus encase the outside faces of the rectilinear tube .legssadjacent the elbow.

Before the shaping operation, the bend A is preferably heated uniformly along the whole shaded portion shown in Figure 2 with the exception of the central part E of the crotch of the bend which will bear against the end parts 15 of the projections 14, 16, of the die halves 10, 12.

To operate the aparatus for shaping of the bend it is sufficient, then, to move the punch 24 in the direction of arrow F into the interior of the die halves. During this movement the elbow takes support in the cold portion E of its crotch on the ends 15 of the projections 14, 16 and the tube legs B, C extending from the elbow are contacted by the fingers 27, 28 of punch 24 and are forced into the semi-cylindrical grooves 20, 21 and 22, 23 of dies 10, 12 until finally, the whole exterior wall surface portion of the elbow is encased in the semi-circular groove 26 in punch 31.

During this shaping movement, the more or less angular shoulders G1, G2 (Fig. 3) which the work piece or elbow may have are beaten down in the outer as well as in the inner portion in such a way that the tube of necessity takes on an accurate semi-circular shape over degrees at the elbow. Moreover, if there is ovalization of the internal portion of the bend, the shaping movement has the effect of restoring to the bend a perfectly circular cross-section. Finally, the two rectilinear tube legs B, C of the bend which might not originally be accurately parallel are straightened by being forcefully applied against the semi-cylindrical grooves 20, 21 and 22, 23 of the projections 14, 16.

In the case of treating a tube bend or bifurcate H having a tube connection 1, as seen in Figure 4, a hollowing out or recess 30 is arranged in punch 31 in such a way as to accommodate and shape at the same time, the tube 1. This hollowing 30 encases the edge of the opening of the tube 1 and can give it, if necessary, a certain chamfer to facilitate Welding of a coupling tube on tube 5*.

On the other hand, in a more general way, the shape of punch 24 is designed according to the shape of the elbow which it is desired to obtain finally, and to the shaping of the elbow to be treated. It is thus that, as has already been proposed in my earlier application Serial No. 233,358 filed June 25, 1951, it is possible, in order to obtain an additional thickness in the outer portion of the bend, to fashion beforehand, either on the bend, or on the straight tube from which the bend is obtained, a bulb, which can later be flattened in such a way that the excess material it has will form an extra thickness on the outer portion of the elbow. When it is a case of treating, with the apparatus of the invention, elbows bulbed in the exterior portion of the bend, it is possible to flatten this bulb during the last shaping operation in order to obtain, finally, a perfectly shaped elbow having an extra thickness in the outer portion of the bend. It is known that such elbows reinforced in the outer portion are especially called for in the case of apparatus where there is wear at the end of the bend, and, for example, in the case of locomotive superheater tubes.

3 What is claimed is:

. 1. Apparatus'for shaping a tube bend comprising; two die halves for receiving the elbow and adjacent tube leg parts of a return bend each having a projection insertible between the tube legs with the ends of the projections supporting the crotch region of the bend and being formed with complementary: portions of a semi-circular groove for engaging the crotch region of the bend and which portions constitute continuations of complementary portions of similarly shaped grooves on the sides of said projections for engaging the confronting parts of the tube legs that merge into the crotch region of the bend, the die halves being .formed outwardly of said projections with guide recesses for receiving the spaced fingers of a punch; and a punch having spaced fingers engageable in said recesses and formed between said fingers with a semi-circular groove for engaging and shaping the end of the bend, said fingers being formed on the faces thereof that confront 4 the die projections with semi-circular grooves engageable with the outer surfaces of the tube legs adjacent the end of the bend and forming continuations of the groove that is located on the punch between said fingers.

2. Apparatus for shaping a tube bend as recited in claim 1 wherein said punch is formed between said fingers thereof with a recess extending outwardly from the groove between said fingers for receiving a projection on the end of said bend.

References Cited in the file of this patent UNITED STATES PATENTS 1,437,918 Smith Dec. 5, 1922 FOREIGN PATENTS 384,465 Great Britain Dec. 8, 1932 

